QUANTITATION OF IMPORTANT ROAST-SMELLING ODORANTS IN POPCORN BY STABLE-ISOTOPE DILUTION ASSAYS AND MODEL STUDIES ON FLAVOR FORMATION DURINGPOPPING

Stable isotope dilution assays were developed for the quantitation of the roast-smelling popcorn odorants, 2-acetyl-tetrahydropyridine (ACTP Y) and 2-propionyl-1-pyrroline (PPY). Both and, in addition, the two f urther roast-aroma compounds, a-acetyl-l-pyrroline (ACPY) and acetylpy razine, were quantified in different popcorn samples. In fresh hot-air popped corn, ACTPY showed the highest concentration (437 mu g/kg), fo llowed by ACPY (24 mu g/kg) which were established as the key contribu tors to the roasty popcorn odor. During storage of a popcorn sample fo r seven days in a sealed polyethylene bag, the concentrations of ACTPY , ACPY, and PPY decreased to about one third. Model studies using aque ous maize extracts and distinct precursor compounds revealed the pair proline/fructose as the most effective precursor system in ACTPY forma tion, while the pair 1-pyrroline/2-oxopropanal was most effective in t he generation of ACPY. A reaction scheme suggesting that ACPY is forme d by an ''acylation'' of the intermediate 1-pyrroline by 2-oxopropanal is discussed.